A coating composition comprising a thermoset resin and a thermoplastic resin

ABSTRACT

A powder coating composition comprising: a) a thermoset resin comprising an acid functional polyester material, b) a thermoplastic resin and c) a crosslinker material, wherein the coating composition is substantially free of bisphenol A (BPA), bisphenol F (BPF), bisphenol A diglycidylether (BADGE) and bisphenol F diglycidyl ether (BFDGE).

The present invention relates to coating compositions. In particular,the present invention relates to coating compositions for coating onto ametal substrate, particularly onto a metal substrate for the packagingindustry, such as coating onto food and/or beverage containers oraerosol cans. The invention also extends to metal substrates coated onat least of portion thereof with the thermoset powder coatingcomposition.

The surfaces of such food and/or beverage container or aerosol cans arecoated for various reasons. The external surfaces of such containers orcans are often coated in a decorative manner and may allow printingthereon to inform a user as to the contents of the container or can. Theinternal surfaces of such container or cans are typically coated toprotect the container or can from the contents therein, which in someinstances may be chemically aggressive. The coating on the container orcan should also protect the contents from the container or can. Thereshould be a minimal amount of alteration to the contents from materialsthat are products of erosion of the container or can, or from thecoating itself. Accordingly, the coating composition used to coat theinternal surfaces of the container or can should be designed such thatit is able to withstand contact with these aggressive chemicals and tominimise the release of material from the metal of the container or canor the coating layer into the contents of the container or can.

A wide variety of coatings have been used to coat the above mentionedcontainers or cans. With regard to food and/or beverage containers, thecoating compositions are required to have certain properties such asbeing capable of high speed application, having excellent adhesion tothe substrate, being safe for food contact and having properties oncecured that are suitable for their end use.

Cans used for the storage of aerosols, such as personal healthcareaerosols, are typically formed from a tube, for example, an aluminiumtube. One such tube type is a monobloc aerosol, which is so calledbecause it is formed from a single piece (a small disc known as a“slug”) of aluminium. Coating compositions known in the art and used tocoat such cans, particularly an internal portion thereof, includepolyamide imide, which is made in N-methyl pyrrolidone. However,N-methyl pyrrolidone has recently been reclassified as toxic toreproduction and development (reprotoxic) and also listed as havingspecific organ toxicity for the respiratory tract and thus its use isnot desirable.

Furthermore, many of the coating compositions currently used for foodand/or beverage or aerosol applications contain epoxy resins. Such epoxyresins are typically formed from polyglycidyl ethers of bisphenol A(BPA). BPA is perceived as being harmful to human health and it istherefore desirable to eliminate it from coatings. Derivatives of BPAsuch as diglycidyl ethers of bisphenol A (BADGE), epoxy novolak resinsand polyols prepared from BPA and bisphenol F (BPF) are also viewed asproblematic.

According to a first aspect of the present invention there is provided apowder coating composition comprising:

-   -   a) a thermoset resin comprising an acid functional polyester        material,    -   b) a thermoplastic resin and    -   c) a crosslinker material,        wherein the coating composition is substantially free of        bisphenol A (BPA), bisphenol F (BPF), bisphenol A diglycidyl        ether (BADGE) and bisphenol F diglycidyl ether (BFDGE).

“Powder” and like terms as used herein, refers to materials that are inthe form of solid particulates, as opposed to materials which are in theliquid form.

The powder coating composition of the present invention is suitably athermoset powder coating composition comprising a thermoset resin.Suitably, the thermoset resin comprises an acid functional polyestermaterial (a). The acid functional polyester material suitably comprisesthe reaction product of a polyacid and a polyol.

“Polyacid” and like terms as used herein, refers to a compound havingtwo or more carboxylic acid groups, such as two, three or four acidgroups, and includes an ester of the polyacid (wherein one or more ofthe acid groups is esterified) or an anhydride. The polyacid is suitablyan organic polyacid.

Suitably, the carboxylic acid groups of the polyacid may be connected bya bridging group selected from: an alkylene group; an alkenylene group;an alkynylene group; or an arylene group.

The acid functional polyester material may be formed from any suitablepolyacid. Suitable examples include, but are not limited to one or moreof the following: diacids such as, for example, maleic acid, fumaricacid, itaconic acid, adipic acid, azelaic acid, succinic acid, sebacicacid, glutaric acid, heptanoic acid, decanoic diacid, dodecanoic diacid,dodecanedioic acid, phthalic acid, isophthalic acid,5-tert-butylisophthalic acid, tetrachlorophthalic acid,tetrahydrophthalic acid, naphthalene dicarboxylic acid, terephthalicacid, hexahydrophthalic acid, methylhexahydrophthalic acid, dimethylterephthalate, cyclohexane dicarboxylic acid, chlorendic anhydride,1,3-cyclohexane dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid,endomethylene tetrahydrophthalic acid and endoethylene hexahydrophthalicacid; triacids such as, for example, trimellitic acid; polyacids suchas, for example, naphthalene tetracarboxylic acid, cyclohexanetetracarboxylic acid, cyclobutane tetracarboxylic and tricyclodecanepolycarboxylic acid; esters and anhydrides of all the aforementionedacids and combinations thereof.

The polyacid may be selected from terephthalic acid; isophthalic acid;adipic acid; trimellitic anhydride; or combinations thereof.

The polyacid may comprise terephthalic acid and/or isophthalic acid. Thepolyacid may comprise at least 50 mol %, suitably at least 60 mol %,such as at least 70 mol %, or even at least 75 mol % of terephthalicacid and/or isophthalic acid based on the total number of moles ofpolyacid. The polyacid may comprise up to 100 mol %, suitably up to 95mol %, such as up to 90 mol % of terephthalic acid and/or isophthalicacid based on the total number of moles of polyacid. The polyacid maycomprise from 50 to 100 mol %, suitably from 60 to 100 mol %, such asfrom 70 to 100 mol %, or even from 75 to 100 mol % of terephthalic acidand/or isophthalic acid based on the total number of moles of polyacid.The polyacid may comprise from 50 to 95 mol %, suitably from 60 to 95mol %, such as from 70 to 95 mol %, or even from 75 to 95 mol % ofterephthalic acid and/or isophthalic acid based on the total number ofmoles of polyacid. The polyacid may comprise from 50 to 90 mol %,suitably from 60 to 90 mol %, such as from 70 to 90 mol %, or even from75 to 90 mol % of terephthalic acid and/or isophthalic acid based on thetotal number of moles of polyacid. Suitably, the polyacid may comprisefrom 75 to 90 mol % of terephthalic acid and/or isophthalic acid basedon the total number of moles of polyacid.

The polyacid may comprise a diacid. The diacid may comprise at least 60mol %, suitably at least 70 mol %, such as at least 80 mol %, or even 85mol % of terephthalic acid and/or isophthalic acid based on the totalnumber of moles of diacid. The diacid may comprise up to 100 mol %,suitably up to 99.9 mol %, such as at least 99 mol %, or even up to 95mol % of terephthalic acid and/or isophthalic acid based on the totalnumber of moles of diacid. The polyacid may comprise from 60 to 100 mol%, suitably from 70 to 100 mol %, such as from 80 to 100 mol %, or evenfrom 80 to 100 mol % of terephthalic acid and/or isophthalic acid basedon the total number of moles of diacid. The polyacid may comprise from60 to 99.9 mol %, suitably from 70 to 99.9 mol %, such as from 80 to99.9 mol %, or even from 80 to 99.9 mol % of terephthalic acid and/orisophthalic acid based on the total number of moles of diacid. Thepolyacid may comprise from 60 to 99 mol %, suitably from 70 to 99 mol %,such as from 80 to 99 mol %, or even from 80 to 99 mol % of terephthalicacid and/or isophthalic acid based on the total number of moles ofdiacid. The polyacid may comprise from 60 to 95 mol %, suitably from 70to 95 mol %, such as from 80 to 95 mol %, or even from 80 to 95 mol % ofterephthalic acid and/or isophthalic acid based on the total number ofmoles of diacid. Suitably, the diacid may comprise from 75 to 100 mol %of terephthalic acid and/or isophthalic acid based on the total numberof moles of diacid.

The acid functional polyester material may be formed from a polyacidcomprising succinic acid, glutaric acid, adipic acid, heptanoic acid,dodecanedioic acid or combinations thereof. Suitably, the acidfunctional polyester material may be formed from a polyacid comprisingsuccinic acid adipic acid, dodecanedioic acid or combinations thereof.It has surprisingly and advantageously been found by the presentinventors that the presence of such polyacids in an acid functionalpolyester material results in a liquid coating composition, comprisingsuch acid functional polyester materials, having a lower curingtemperature than would typically be expected. It will be understood by aperson skilled in the art that this is advantageous industrially andenvironmentally.

“Polyol” and like terms, as used herein, refers to a compound having twoor more hydroxyl groups, such as two, three or four hydroxyl groups. Thehydroxyl groups of the polyol may be connected by a bridging groupselected from: an alkylene group; an alkenylene group; an alkynylenegroup; or an arylene group. Suitably the polyol is an organic polyol.

The acid functional polyester material may be formed from any suitablepolyol. Suitable examples include, but are not limited to one or more ofthe following: diols such as, for example, alkylene glycols, such asethylene glycol, diethylene glycol, dipropylene glycol, triethyleneglycol, tripropylene glycol, hexylene glycol, polyethylene glycol,polypropylene glycol and neopentyl glycol; hydrogenated bisphenol A;cyclohexanediol; propanediols including 1,2-propanediol,1,3-propanediol, butyl ethyl propanediol and2-ethyl-2-butyl-1,3-propanediol; butanediols including 1,4-butanediol,1,3-butanediol, butane-2,3-diol, 2-methyl-1,3-propanediol,tricyclodecane dimethanol-2,2,4,4-tetramethyl cyclobutane-1,3-diol and2-ethyl-1,4-butanediol; pentanediols including trimethyl pentanediol and2-methylpentanediol; cyclohexanedimethanol; hexanediols including1,6-hexanediol, caprolactonediol (for example, the reaction product ofepsilon-capro lactone and ethylene glycol); hydroxyalkylated bisphenols;polyether glycols, for example, poly(oxytetramethylene) glycol;dimethylol cyclohexane; triols such as, for example, trimethylolpropane, trimethylol ethane, trimethylol butane and glycerol; polyolssuch as, for example, pentaerythritol and di-pentaerythritol; and thelike or combinations thereof.

The polyester material may be formed from an unsaturated polyol.Suitable examples of unsaturated polyols include, but are not limited toone or more of the following: trimethylol propane monoallyl ether;trimethylol ethane monoallyl ether; prop-1-ene-1,3-diol or combinationsthereof.

The polyol may be selected from neopentyl glycol; ethylene glycol;diethylene glycol; or combinations thereof.

The polyol may comprise neopentyl glycol. The polyol may comprise atleast 10 mol %, suitably at least 20 mol %, such as at least 30 mol %,such as 40 mol %, or even at least 50 mol % of neopentyl glycol based onthe total number of moles of polyol. The polyol may comprise up to 100mol %, suitably up to 90 mol %, such as up to 80 mol %, or even up to 70mol % of neopentyl glycol based on the total number of moles of polyolpresent. The polyol may comprise from 10 to 100 mol %, suitably from 10to 90 mol %, such as from 10 to 80 mol %, or even from 10 to 70 mol % ofneopentyl glycol based on the total number of moles of polyol present.The polyol may comprise from 20 to 100 mol %, suitably from 20 to 90 mol%, such as from 20 to 80 mol %, or even from 20 to 70 mol % of neopentylglycol based on the total number of moles of polyol present. The polyolmay comprise from 30 to 100 mol %, suitably from 30 to 90 mol %, such asfrom 30 to 80 mol %, or even from 30 to 70 mol % of neopentyl glycolbased on the total number of moles of polyol present. The polyol maycomprise from 40 to 100 mol %, suitably from 40 to 90 mol %, such asfrom 40 to 80 mol %, or even from 40 to 70 mol % of neopentyl glycolbased on the total number of moles of polyol present. The polyol maycomprise from 50 to 100 mol %, suitably from 50 to 90 mol %, such asfrom 50 to 80 mol %, or even from 50 to 70 mol % of neopentyl glycolbased on the total number of moles of polyol present. Suitably, thepolyol may comprise from 50 to 70 mol % of neopentyl glycol based on thetotal number of moles of polyol present.

The polyol may comprise a diol. The diol may comprise at least 10 mol %,suitably at least 20 mol %, such as at least 30 mol %, such as 40 mol %,or even at least 50 mol % of neopentyl glycol based on the total numberof moles of diol. The diol may comprise up to 100 mol %, suitably up to90 mol %, such as up to 80 mol %, or even up to 70 mol % of neopentylglycol based on the total number of moles of diol present. The diol maycomprise from 10 to 100 mol %, suitably from 10 to 90 mol %, such asfrom 10 to 80 mol %, or even from 10 to 70 mol % of neopentyl glycolbased on the total number of moles of diol present. The diol maycomprise from 20 to 100 mol %, suitably from 20 to 90 mol %, such asfrom 20 to 80 mol %, or even from 20 to 70 mol % of neopentyl glycolbased on the total number of moles of diol present. The diol maycomprise from 30 to 100 mol %, suitably from 30 to 90 mol %, such asfrom 30 to 80 mol %, or even from 30 to 70 mol % of neopentyl glycolbased on the total number of moles of diol present. The diol maycomprise from 40 to 100 mol %, suitably from 40 to 90 mol %, such asfrom 40 to 80 mol %, or even from 40 to 70 mol % of neopentyl glycolbased on the total number of moles of diol present. The diol maycomprise from 50 to 100 mol %, suitably from 50 to 90 mol %, such asfrom 50 to 80 mol %, or even from 50 to 70 mol % of neopentyl glycolbased on the total number of moles of diol present. Suitably, the diolmay comprise from 50 to 70 mol % of neopentyl glycol based on the totalnumber of moles of diol present.

The term “alk” or “alkyl”, as used herein unless otherwise defined,relates to saturated hydrocarbon radicals being straight, branched,cyclic or polycyclic moieties or combinations thereof and contain 1 to20 carbon atoms, suitably 1 to 10 carbon atoms, more suitably 1 to 8carbon atoms, still more suitably 1 to 6 carbon atoms, yet more suitably1 to 4 carbon atoms. These radicals may be optionally substituted with achloro, bromo, iodo, cyano, nitro, OR¹⁹, OC(O)R²⁰, C(0)R²¹, C(O)OR²²,NR²³R²⁴, C(O)NR²⁶R²⁶, SR²⁷, C(O)SR²⁷, C(S)NR²⁵R²⁶, aryl or Het, whereinR¹⁹ to R²⁷ each independently represent hydrogen, aryl or alkyl, and/orbe interrupted by one or more oxygen or sulphur atoms, or by silano ordialkylsiloxane groups. Examples of such radicals may be independentlyselected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, 2-methylbutyl, pentyl, iso-amyl, hexyl,cyclohexyl, 3-methylpentyl, octyl and the like. The term “alkylene”, asused herein, relates to a bivalent radical alkyl group as defined above.For example, an alkyl group such as methyl which would be represented as—CH₃, becomes methylene, —CH₂—, when represented as an alkylene. Otheralkylene groups should be understood accordingly.

The term “alkenyl”, as used herein, relates to hydrocarbon radicalshaving one or several, suitably up to 4, double bonds, being straight,branched, cyclic or polycyclic moieties or combinations thereof andcontaining from 2 to 18 carbon atoms, suitably 2 to 10 carbon atoms,more suitably from 2 to 8 carbon atoms, still more suitably 2 to 6carbon atoms, yet more suitably 2 to 4 carbon atoms. These radicals maybe optionally substituted with a hydroxyl, chloro, bromo, iodo, cyano,nitro, OR¹⁹, OC(O)R²⁰, C(O)R²¹, C(O)OR²², NR²³R²⁴, C(O)NR²⁵R²⁶, SR²⁷,C(O)SR²⁷, C(S)NR²⁵R²⁶, or aryl, wherein R¹⁹ to R²⁷ each independentlyrepresent hydrogen, aryl or alkyl, and/or be interrupted by one or moreoxygen or sulphur atoms, or by silano or dialkylsiloxane groups.Examples of such radicals may be independently selected from alkenylgroups include vinyl, allyl, isopropenyl, pentenyl, hexenyl, heptenyl,cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclohexenyl, 1-propenyl,2-butenyl, 2-methyl-2-butenyl, isoprenyl, farnesyl, geranyl,geranylgeranyl and the like. The term “alkenylene”, as used herein,relates to a bivalent radical alkenyl group as defined above. Forexample, an alkenyl group such as ethenyl which would be represented as—CH═CH2, becomes ethenylene, —CH═CH—, when represented as an alkenylene.Other alkenylene groups should be understood accordingly.

The term “alkynyl”, as used herein, relates to hydrocarbon radicalshaving one or several, suitably up to 4, triple bonds, being straight,branched, cyclic or polycyclic moieties or combinations thereof andhaving from 2 to 18 carbon atoms, suitably 2 to 10 carbon atoms, moresuitably from 2 to 8 carbon atoms, still more suitably from 2 to 6carbon atoms, yet more suitably 2 to 4 carbon atoms. These radicals maybe optionally substituted with a hydroxy, chloro, bromo, iodo, cyano,nitro, OR¹⁹, OC(O)R²⁰, C(O)R²¹, C(O)OR²², NR²³ _(R) ²⁴, C(O)NR²⁵R²⁶,SR²⁷, C(O)SR²⁷, C(S)NR²⁶R²⁶, or aryl, wherein R¹⁹ to R²⁷ eachindependently represent hydrogen, aryl or lower alkyl, and/or beinterrupted by one or more oxygen or sulphur atoms, or by silano ordialkylsiloxane groups. Examples of such radicals may be independentlyselected from alkynyl radicals include ethynyl, propynyl, propargyl,butynyl, pentynyl, hexynyl and the like. The term “alkynylene”, as usedherein, relates to a bivalent radical alkynyl group as defined above.For example, an alkynyl group such as ethynyl which would be representedas —C≡CH, becomes ethynylene, —C≡C—, when represented as an alkynylene.Other alkynylene groups should be understood accordingly.

The term “aryl” as used herein, relates to an organic radical derivedfrom an aromatic hydrocarbon by removal of one hydrogen, and includesany monocyclic, bicyclic or polycyclic carbon ring of up to 7 members ineach ring, wherein at least one ring is aromatic. These radicals may beoptionally substituted with a hydroxy, chloro, bromo, iodo, cyano,nitro, OR¹⁹, OC(O)R²⁰, C(O)R²¹, C(O)OR²², NR²³R²⁴, C(O)NR²⁵R²⁶, SR²⁷,C(O)SR²⁷, C(S)NR²⁵R²⁶, or aryl, wherein R¹⁹ to R²⁷ each independentlyrepresent hydrogen, aryl or lower alkyl, and/or be interrupted by one ormore oxygen or sulphur atoms, or by silano or dialkylsilcon groups.Examples of such radicals may be independently selected from phenyl,p-tolyl, 4-methoxyphenyl, 4-(tert-butoxy)phenyl,3-methyl-4-methoxyphenyl, 4-fluorophenyl, 4-chlorophenyl, 3-nitrophenyl,3-aminophenyl, 3-acetamidophenyl, 4-acetamidophenyl,2-methyl-3-acetamidophenyl, 2-methyl-3-aminophenyl,3-methyl-4-aminophenyl, 2-amino-3-methylphenyl,2,4-dimethyl-3-aminophenyl, 4-hydroxyphenyl, 3-methyl-4-hydroxyphenyl,1-naphthyl, 2-naphthyl, 3-amino-1-naphthyl, 2-methyl-3-amino-1-naphthyl,6-amino-2-naphthyl, 4,6-dimethoxy-2-naphthyl, tetrahydronaphthyl,indanyl, biphenyl, phenanthryl, anthryl or acenaphthyl and the like. Theterm “arylene”, as used herein, relates to a bivalent radical aryl groupas defined above. For example, an aryl group such as phenyl which wouldbe represented as -Ph, becomes phenylene, -Ph-, when represented as anarylene. Other arylene groups should be understood accordingly.

For the avoidance of doubt, the reference to alkyl, alkenyl, alkynyl,aryl or aralkyl in composite groups herein should be interpretedaccordingly, for example the reference to alkyl in aminoalkyl or alk inalkoxyl should be interpreted as alk or alkyl above etc.

As used herein, unless otherwise expressly specified, all numbers suchas those expressing values, ranges, amounts or percentages may be readas if prefaced by the word “about”, even if the term does not expresslyappear. Also, any numerical range recited herein is intended to includeall sub-ranges subsumed therein. Singular encompasses plural and viceversa. For example, although reference is made herein to, for example,“a” thermoset resin, “a” thermoplastic resin, “a” crosslinker, “an”alkanol amine, “the” residue of “an”, and the like, one or more of eachof these and any other components can be used. As used herein, the term“polymer” refers to oligomers and both homopolymers and copolymers, andthe prefix “poly” refers to two or more. Including, for example and liketerms means including for example but not limited to. When ranges aregiven, any endpoints of those ranges and/or numbers within those rangescan be.

The acid functional polyester material may be formed from any suitablemolar ratio of polyacid to polyol. The molar ratio of polyacid to polyolin the polyester material may be from 20:1 to 1:20, suitably from 10:1to 1:10, such as from 5:1 to 1:5, or even from 2:1 to 1:2. Suitably, themolar ratio of polyacid to polyol in the polyester material may be 1:1.

The acid functional polyester material may comprise a polyol comprisinga diacid and a triacid and a diol. It will be appreciated by a personskilled in the art that the amount of triacid present will influence theacid number of the acid functional polyester material.

The acid functional polyester material may optionally be formed from oneor more additional monomers. Suitably, the acid functional polyestermaterial may optionally include one or more additional monomers selectedfrom monoacids or monohydric alcohols or combinations thereof. Suitably,the optional additional monomers may be organic.

The acid functional polyester material may optionally be formed from anadditional monoacid. “Monoacid”, and like terms as used herein, refersto compounds having one carboxylic acid group and includes an ester ofthe monoacid (where the acid group is esterified) or an anhydride. Themonoacid is suitably an organic monoacid.

The acid functional polyester material may optionally be formed from anysuitable additional monoacid. Suitable examples include, but are notlimited to one or more of the following: benzoic acid; cyclohexanecarboxylic acid; tricyclodecane carboxylic acid; camporic acid; benzoicacid; t-butyl benzoic acid; C₁-C₁₈ aliphatic carboxylic acids such asacetic acid; propanoic acid; butanoic acid; hexanoic acid; oleic acid;linoleic acid; undecanoic acid; lauric acid; isononanoic acid; fattyacids; hydrogenated fatty acids of naturally occurring oils; estersand/or anhydrides of any of the aforementioned acids and combinationsthereof.

The acid functional polyester material may optionally be formed from anadditional monohydric alcohol. “Monohydric alcohol” and like terms asused herein, refers to compounds having one hydroxyl group. Suitably,the monohydric alcohol is an organic monohydric alcohol.

The acid functional polyester material may optionally be formed from anysuitable additional monohydric alcohol. Suitable examples include butare not limited to one or more of the following: benzyl alcohol;hydroxyethoxybenzene; methanol; ethanol; propanol; butanol; pentanol;hexanol; heptanol; dodecyl alcohol; stearyl alcohol; oleyl alcohol;undecanol; cyclohexanol; phenol; phenyl carbinol; methylphenyl carbinol;cresol; monoethers of glycols; halogen-substituted or other substitutedalcohols and combinations thereof.

The acid functional polyester material may have an acid number (AN) ofat least 25 mg KOH/g. Suitably, the polyester material may have an acidnumber from 25 to 100 mg KOH/g, such as from 30 to 100 mg KOH/g or evenfrom 50 to 90 mg KOH/g. The acid functional polyester material may havean acid number from 50 to 80 mg KOH/g.

The acid functional polyester material may have an acid number from 65to 75 mg KOH/g. The acid functional polyester material may have an acidnumber from 30 to 40 mg KOH/g.

Suitably, the acid number (AN) is expressed on solids.

The acid number (AN) of the acid functional polyester material may bemeasured by any suitable method. Methods to measure AN will be wellknown to a person skilled in the art. In such a method, suitably, the ANis determined by titration with 0.1M methanolic potassium hydroxide(KOH) solution. A sample of solid polyester (typically, 0.1 to 3 g) isweighed accurately into a conical flask and is dissolved, using lightheating and stirring as appropriate, in 25 ml of dimethyl formamidecontaining phenolphthalein indicator. The solution is then cooled toroom temperature and titrated with the 0.1M methanolic potassiumhydroxide solution. The resulting acid number is expressed in units ofmg KOH/g and is calculated using the following equation:

${{Acid}\mspace{14mu} {number}} = \frac{\begin{matrix}{{titre}\mspace{14mu} {of}\mspace{14mu} {KOH}\mspace{14mu} {solution}\mspace{14mu} ({ml}) \times} \\{{molarity}\mspace{14mu} {KOH}\mspace{14mu} {solution}\mspace{14mu} (M) \times 56.1}\end{matrix}}{{weight}\mspace{14mu} {of}\mspace{14mu} {solid}\mspace{14mu} {sample}\mspace{14mu} (g)}$

All values for acid number (AN) reported herein were measured this way.

The acid functional polyester material may have any suitable grosshydroxyl value (OHV). The acid functional polyester material may have agross OHV up to 5.0 mg KOH/g. Suitably, the acid functional polyestermaterial may have a gross OHV from 0 to 5.0 mg KOH/g, such as from 0 to0.4 KOH/g or even from 0 to 3.0 KOH/g.

Suitably, the gross hydroxyl value (OHV) is expressed on solids.

The gross hydroxyl value (OHV) of the acid functional polyester materialmay be measured by any suitable method. Methods to measure OHV will bewell known to a person skilled in the art. Suitably, the hydroxyl valueis the number of mg of KOH equivalent to the hydroxyl groups in 1 g ofmaterial. In such as method, suitably, a sample of solid polyester(typically, 0.1 to 3 g) is weighed accurately into a conical flask andis dissolved, using light heating and stirring as appropriate, in 20 mlof tetrahydrofuran. 10 ml of 0.1M 4-(dimethylamino)pyridine intetrahydrofuran (catalyst solution) and 5 ml of a 9 vol % solution ofacetic anhydride in tetrahydrofuran (i.e. 90 ml acetic anhydride in 910ml tetrahydrofuran; acetylating solution) are then added to the mixture.After 5 minutes, 10 ml of an 80 vol % solution of tetrahydrofuran (i.e.4 volume parts tetrahydrofuran to 1 part distilled water; hydrolysissolution) us added. After 15 minutes, 10 ml tetrahydrofuran is added andthe solution is titrated with 0.5M ethanolic potassium hydroxide (KOH).A blank sample is also run where the sample of solid polyester isomitted. The resulting hydroxyl number is expressed in units of mg KOH/gand is calculated using the following equation:

${{Hydroxyl}\mspace{14mu} {value}} = \frac{\left( {V_{2} - V_{1}} \right) \times {molarity}\mspace{14mu} {of}\mspace{14mu} {KOH}\mspace{14mu} {solution}\mspace{14mu} (M) \times 56.1}{{weight}\mspace{14mu} {of}\mspace{14mu} {solid}\mspace{14mu} {sample}\mspace{14mu} (g)}$

wherein V₁ is the titre of KOH solution (ml) of the polyester sample andV₂ is the titre of KOH solution (ml) of the blank sample.

All values for gross hydroxyl value (OHV) reported herein were measuredthis way.

The acid functional polyester material may have any suitable glasstransition temperature (Tg). The acid functional polyester material mayhave a Tg of at least 20° C., suitably at least 30° C., such as at least40° C., or even at least 50° C. The acid functional polyester materialmay have a Tg of up to 150° C., suitably up to 120° C., such as up to100° C., or even up to 80° C. The acid functional polyester material mayhave a Tg from 20° C. to 150° C., suitably from 20° C. to 120° C., suchas from 20° C. to 100° C., or even from 20° C. to 80° C. The acidfunctional polyester material may have a Tg from 30° C. to 150° C.,suitably from 30° C. to 120° C., such as from 30° C. to 100° C., or evenfrom 30° C. to 80° C. The acid functional polyester material may have aTg from 40° C. to 150° C., suitably from 40° C. to 120° C., such as from40° C. to 100° C., or even from 40° C. to 80° C. The acid functionalpolyester material may have a Tg from 50° C. to 150° C., suitably from50° C. to 120° C., such as from 50° C. to 100° C., or even from 50° C.to 80° C.

Suitably, the acid functional polyester material may have a Tg from 60°C. to 70° C.

The Tg of the acid functional polyester material may be measured by anysuitable method. Methods to measure Tg will be well known to a personskilled in the art. Suitably, the Tg is measured according to ASTMD6604-00(2013) (“Standard Practice for Glass Transition Temperatures ofHydrocarbon Resins by Differential Scanning Calorimetry”. Heat-fluxdifferential scanning calorimetry (DSC), sample pans: aluminium,reference: blank, calibration: indium and mercury, sample weight: 10 mg,heating rate: 20° C./min). All values for glass transition temperature(Tg) reported herein were measured this way.

The acid functional polyester material according to the first aspect ofthe present invention may have any suitable melt viscosity at 200° C.The acid functional polyester material may have a melt viscosity at 200°C. from 2 to 100 Poise, suitably from 5 to 70 Poise, such as from 10 to50 Poise, or even from 20 to 40 Poise. The acid functional polyestermaterial may have a melt viscosity at 200° C. of at least 2 Poise,suitably at least 5 Poise, such as at least 10 Poise, or even at least20 Poise. The acid functional polyester material may have a meltviscosity at 200° C. of up to 100 Poise, suitably up to 70 Poise, suchas up to 50 Poise, or even up to 40 Poise. The acid functional polyestermaterial may have a melt viscosity at 200° C. from 2 to 100 Poise,suitably from 2 to 70 Poise, such as from 2 to 50 Poise, or even from 2to 40 Poise. The acid functional polyester material may have a meltviscosity at 200° C. from 5 to 100 Poise, suitably from 5 to 70 Poise,such as from 5 to 50 Poise, or even from 5 to 40 Poise. The acidfunctional polyester material may have a melt viscosity at 200° C. from10 to 100 Poise, suitably from 10 to 70 Poise, such as from 10 to 50Poise, or even from 10 to 40 Poise. The acid functional polyestermaterial may have a melt viscosity at 200° C. from 20 to 100 Poise,suitably from 20 to 70 Poise, such as from 20 to 50 Poise, or even from20 to 40 Poise.

The melt viscosity of the acid functional polyester material may bemeasured by any suitable method. Methods to measure melt viscosity willbe well known to a person skilled in the art. Suitably, melt viscosityis determined using a cone and plate viscometer with a heated plate withcones which can be selected together with appropriate rotational speedsto measure viscosities within the desired ranges. Suitably, a BrookfieldCAP 2000+machine which is capable of measuring viscosities attemperatures of 100 to 250° C. is used. The temperature selected for themeasurement is held constant throughout the measurement time and thedetail of the temperature used is suitably recorded for eachmeasurement. Suitably, the cone used is a spindle no. 6 and the speed ofrotation is selected so as to ensure that the range of measurementsfalls well within the total measurement range. All values for meltviscosity reported herein were measured this way.

The acid functional polyester material of the present invention may haveany suitable number-average molecular weight (Mn). The acid functionalpolyester material may have an Mn from 500 Daltons (Da=g/mole), suitablyfrom 1,000 Da, such as from 2,000 Da or even from 5,000 Da. The acidfunctional polyester material may have an Mn up to 200,000 Da, suitablyup to 100,000 Da, such as up to 50,000 Da or even up to 20,000 Da.

The acid functional polyester material may have an Mn from 500 to200,000 Da, suitably from 1,000 to 200,000 Da, such as from 2,000 to200,000 Da or even from 5,000 to 200,000 Da. The acid functionalpolyester material may have an Mn from 500 to 100,000 Da, suitably from1,000 to 100,000 Da, such as from 2,000 to 100,000 Da or even from 5,000to 100,000 Da. The acid functional polyester material may have an Mnfrom 500 to 50,000 Da, suitably from 1,000 to 50,000 Da, such as from2,000 to 50,000 Da or even from 5,000 to 50,000 Da. The acid functionalpolyester material may have an Mn from 500 to 20,000 Da, suitably from1,000 to 20,000 Da, such as from 2,000 to 20,000 Da or even from 5,000to 20,000 Da.

The number-average molecular weight (Mn) may be measured by any suitablemethod. Techniques to measure the number-average molecular weight willbe well known to a person skilled in the art. Suitably, the Mn may bedetermined by gel permeation chromatography using a polystyrene standardaccording to ASTM D6579-11(“Standard Practice for Molecular WeightAverages and Molecular Weight Distribution of Hydrocarbon, Rosin andTerpene Resins by Size Exclusion Chromatography”. UV detector; 254 nm,solvent: unstabilised THF, retention time marker: toluene, sampleconcentration: 2 mg/ml). All values for number-average molecular weight(Mn) reported herein were measured this way.

The acid functional polyester material of the present invention may haveany suitable weight-average molecular weight (Mw). The acid functionalpolyester material may have an Mw from 500 Daltons (Da=g/mole), suitablyfrom 1,000 Da, such as from 2,000 Da or even from 5,000 Da. The acidfunctional polyester material may have an Mw up to 200,000 Da, suitablyup to 100,000 Da, such as up to 50,000 Da or even up to 20,000 Da.

The acid functional polyester material may have an Mw from 500 to200,000 Da, suitably from 1,000 to 200,000 Da, such as from 2,000 to200,000 Da or even from 5,000 to 200,000 Da. The acid functionalpolyester material may have an Mw from 500 to 100,000 Da, suitably from1,000 to 100,000 Da, such as from 2,000 to 100,000 Da or even from 5,000to 100,000 Da. The acid functional polyester material may have an Mwfrom 500 to 50,000 Da, suitably from 1,000 to 50,000 Da, such as from2,000 to 50,000 Da or even from 5,000 to 50,000 Da. The acid functionalpolyester material may have an Mw from 500 to 20,000 Da, suitably from1,000 to 20,000 Da, such as from 2,000 to 20,000 Da or even from 5,000to 20,000 Da.

A person skilled in the art will appreciate that techniques to measurethe number-average molecular weight may also be applied to measure theweight-average molecular weight. All values for weight-average molecularweight (Mw) reported herein were measured this way.

The acid functional polyester material according to any aspect of thepresent invention may be in solid form at room temperature and atatmospheric pressure.

The acid functional polyester material of the present invention may havea glass transition temperature (Tg) from 50 to 100° C. and a viscosityfrom 10 to 50 Poise at 200° C.

The coating compositions of the present invention comprise athermoplastic resin (b). The coating compositions may comprise anysuitable thermoplastic resin. Suitable examples of thermoplastic resinsinclude, but are not limited to, one or more of the following: epoxyresins; polyester resins; polyolefin resins; polyurethane resins;polysiloxane resins; acrylic resins; hydrocarbon resins; polyamide orcombinations thereof. Suitably, the thermoplastic resin may comprisepolyolefin resins, acrylic resins or a combination thereof.

The thermoplastic resin may comprise a polyolefin resin.

The thermoplastic resin may comprise an acrylic resin.

The thermoplastic resin may comprise a polyolefin resin and an acrylicresin.

The thermoplastic resin of the present invention may have any suitableglass transition temperature (Tg). The thermoplastic resin may have a Tgof at least 20° C., suitably at least 25° C., such as at least 30° C.,or even at least 40° C. The thermoplastic resin may have a Tg of up to150° C., suitably up to 120° C., such as up to 100° C., or even up to80° C. The thermoplastic resin may have a Tg from 20° C. to 150° C.,suitably from 20° C. to 120° C., such as from 20° C. to 100° C., or evenfrom 20° C. to 80° C. The thermoplastic resin may have a Tg from 25° C.to 150° C., suitably from 25° C. to 120° C., such as from 25° C. to 100°C., or even from 25° C. to 80° C. The thermoplastic resin may have a Tgfrom 30° C. to 150° C., suitably from 30° C. to 120° C., such as from30° C. to 100° C., or even from 30° C. to 80° C. The thermoplastic resinmay have a Tg from 40° C. to 150° C., suitably from 40° C. to 120° C.,such as from 40° C. to 100° C., or even from 40° C. to 80° C.

Suitably, the thermoplastic resin may have a Tg from 40 to 80° C.

The thermoplastic resin may have a Tg from 40 to 70° C.

The Tg of the thermoplastic resin may be measured by any suitablemethod. Methods to measure Tg will be well known to a person skilled inthe art. Suitably, the Tg is measured according to ASTM D6604-00(2013)(“Standard Practice for Glass Transition Temperatures of HydrocarbonResins by Differential Scanning calorimetry”. Heat-flux differentialscanning calorimetry (DSC), sample pans: aluminium, reference: blank,calibration: indium and mercury, sample weight: 10 mg, heating rate: 20°C./min). All glass transition temperatures (Tg) reported herein weremeasured this way.

The thermoplastic resin of the present invention may have any suitablenumber-average molecular weight (Mn).

The number-average molecular weight may be measured by any suitablemethod. Techniques to measure the number-average molecular weight willbe well known to a person skilled in the art. Suitably, the Mn may bedetermined by gel permeation chromatography using a polystyrene standardaccording to ASTM D6579-11(“Standard Practice for Molecular WeightAverages and Molecular Weight Distribution of Hydrocarbon, Rosin andTerpene Resins by Size Exclusion Chromatography”. UV detector; 254 nm,solvent: unstabilised THF, retention time marker: toluene, sampleconcentration: 2mg/ml). All values for number-average molecular weight(Mn) reported herein were measured this way.

The thermoplastic resin of the present invention may have any suitableweight-average molecular weight (Mw).

A person skilled in the art will appreciate that techniques to measurethe number-average molecular weight may also be applied to measure theweight-average molecular weight. All values for weight-average molecularweight (Mw) reported herein were measured this way.

The thermoplastic resin of the present invention suitably has a meltindex (MI) between 2 and 50 g per 10 min. Where the thermoplastic resincomprises polyamide, the polyamide suitable has a melt index of between27 and 50 g per 10 min.

The melt index is measured according to ISO 1133-1:2011 method B(displacement-measurement method) at a temperature of 230° C. and anominal load of 2.66 kg. All values for melt index reported herein weremeasured this way.

A person skilled in the art will appreciate that techniques to measurethe melt viscosity of the acid functional polyester material may also beapplied to measure the melt viscosity of the thermoplastic resin. Allvalues for melt index reported herein were measured this way.

The thermoset powder coating composition of the present invention maycomprise a commercially available thermoplastic resin such as, nylonresins or for example, those available under the trade name Surlyn(available from DuPont).

The thermoplastic resin may be provided in the form of a granular solidor in the form of a dispersion in a liquid carrier.

When the thermoplastic resin is provided in the form of a granularsolid, the granular solid may be formed by any suitable method. Thegranular solid thermoplastic resin, may be extruded in combination withthe thermoset material. Suitable methods will be well known to a personskilled in the art. Suitably, the extruded thermoset and thermoplasticresin is ground to a powder.

The thermoplastic resin may comprise a polyolefin resin granular solid.

The thermoplastic resin may comprise an acrylic resin granular solid.

The thermoplastic resin may comprise a polyolefin resin granular solidand an acrylic resin granular solid.

For the avoidance of doubt, a dispersion as described herein is agranular solid phase, such as a powder, suspended in a liquid carrier.The liquid carrier, when present, may comprise water, an organicsolvent, a mixture of water and one or more organic solvent(s) or amixture of organic solvents. Suitably, the liquid carrier may comprisewater.

It has surprisingly and advantageously been found by the presentinventors that the acid functional polyester materials of the presentinvention are hydrolytically stable.

Suitable organic solvents include, but are not limited to one or more ofthe following: aliphatic hydrocarbons such as mineral spirits and highflash point naphtha; aromatic hydrocarbons such as benzene; toluene;xylene; solvent naphtha 100, 150, 200; those available from Exxon-MobilChemical Company under the SOLVESSO trade name; alcohols such asethanol; n-propanol; isopropanol; and n-butanol; ketones such asacetone; cyclohexanone; methylisobutyl ketone; methyl ethyl ketone;esters such as ethyl acetate; butyl acetate; n-hexyl acetate; glycolssuch as butyl glycol; glycol ethers such as methoxypropanol; ethyleneglycol monomethyl ether; ethylene glycol monobutyl ether andcombinations thereof.

The thermoplastic resin may comprise a polyolefin resin, an acrylicresin or a combination thereof dispersed in a liquid carrier. Suitably,the thermoplastic resin may comprise a polyolefin resin, an acrylicresin or a combination thereof dispersed in water.

The thermoplastic resin may comprise a polyolefin resin dispersed in aliquid carrier, suitably dispersed in water.

The thermoplastic resin may comprise an acrylic resin dispersed in aliquid carrier, suitably dispersed in water.

The thermoplastic resin may comprise a polyolefin resin and an acrylicresin dispersed in a liquid carrier, suitably dispersed in water.

It will be appreciated by a person skilled in the art that when thethermoplastic resin is provided in the form of a dispersion, the liquidcarrier must be removed in order to form the powder coating compositionsof the present invention. When the thermoplastic resin is provided inthe form of a dispersion, the liquid carrier may be removed prior to theformation of the powder coating composition or during the formation ofthe powder coating composition. Suitably, the liquid carrier may beremoved prior to the formation of the powder coating composition.

The powder coating composition of the present invention comprises acrosslinker material. The crosslinker material may comprise any suitablecrosslinker material. Suitable crosslinker materials will be well knownto the person skilled in the art. Suitable crosslinker materialsinclude, but are not limited to, one or more of the following: phenolicresins (or phenol-formaldehyde resins); aminoplast resins (ortriazine-formaldehyde resins); amino resins; epoxy resins; epoxy-mimicresins, such as those based on bisphenols and other bisphenol A (BPA)replacements; isocyanate resins, isocyanurate resins, such astriglycidylisocyanurate; hydroxy (alkyl) amide resins, such as β-hydroxy(alkyl) amide resins; hydroxy(alkyl) urea resins; carbodiimide resins;oxazolines; polyamines; polyamides and combinations thereof.

The crosslinker material may be selected from hydroxy (alkyl) amideresins, such as β-hydroxy (alkyl) amide resins; hydroxy(alkyl) urearesins; carbodiimide resins; oxazolines; isocyanurate resins, such astriglycidylisocyanurate; epoxy-mimic resins, such as those based onbisphenols and other bisphenol A (BPA) replacements; or combinationsthereof. Suitably, the crosslinker material may be selected from hydroxy(alkyl) amide resins, such as β-hydroxy (alkyl) amide resins;hydroxy(alkyl) urea resins; or combinations thereof.

Suitably, the crosslinker material comprises a hydroxyalkylamidematerial and/or a hydroxyalkylurea material and/or a carbodiimide resin.Suitably, the crosslinker material comprises a hydroxyalkylamidematerial and/or a hydroxyalkylurea material.

Suitably, the crosslinker material may be operable to crosslink the acidfunctionality on the acid functional polyester material.

The crosslinker material may contain nitrogen. The crosslinker materialmay be in the form of an amine or amide material. The crosslinkermaterial may comprise a hydroxyl substituted amine or amide material.

Suitably, the crosslinker material may comprise a hydroxyalkylamidematerial, such as a β-hydroxyalkylamide material.

The crosslinker material may contain a terminal chemical group as shownin Formula I.

wherein R¹ represents an electron withdrawing group, such as (═O);

and Y¹ and Y² each, independently, represents a C₁ to C₃ alkylene group.

The terminal chemical group of Formula I may be connected to a furtherchemical structure, not shown. Additionally or alternatively, thechemical group of formula I may be suspended from a carrier substrate,such as a silica carrier substrate, for example.

The hydroxyalkylamide crosslinker may contain a plurality of terminalchemical groups as shown in Formula I. For example, thehydroxyalkylamide crosslinker may contain 2, 3 or 4 terminal chemicalgroups as shown in Formula I.

The hydroxyalkylamide crosslinker may comprise a moiety according toFormula II:

wherein R¹ and R² with reference to Formula II each, independently,represent an electron withdrawing group, such as (═O); Y¹, Y², Y³ and Y⁴with reference to Formula II each, independently, represent a C₁ to C₃alkylene group; and X is a C₂ to C₆ alkylene group.

Suitably, each of R¹ and R² with reference to Formula II represents a(═O) group.

Suitably, each of Y1, Y2, Y3 and Y4 with reference to Formula IIrepresent an ethylene group.

Suitably, X represents a butylene group.

Accordingly, the hydroxyalkylamide crosslinker comprises a material offormula III:

The coating composition of the present invention may comprise acommercially available hydroxyalkylamide crosslinker such as, forexample, PRIMID XL-552 (available from EMS Chemie); PRIMID QM-1260(available from EMS Chemie); PRIMID SF-4510 (available from EMS Chemie)and N,N,N′,N′-tetrakis(2-hydroxypropyl)adipamide.

The crosslinker may be in the form of a urea material. The crosslinkermay comprise a hydroxyl substituted urea material.

Suitably, the crosslinker may comprise a hydroxy functional alkylpolyurea material.

The crosslinker may contain a terminal chemical group as shown inFormula IV.

wherein Y⁵ and Y⁶ each, independently, represent hydrogen, an alkyl or ahydroxy functional alkyl having two or more carbon atoms and at leastone of Y⁵ and Y⁶ is a hydroxyl functional alkyl having two or morecarbon atoms.

The Y⁵ and Y⁶ groups may exclude ether linkages.

The terminal chemical group of Formula IV may be connected to a furtherchemical structure, not shown. Additionally or alternatively, thechemical group of Formula IV may be suspended from a carrier substrate,such as a silica carrier substrate, for example.

The crosslinker may contain a plurality of terminal chemical groups asshown in Formula IV. For example, the crosslinker may contain 2 to 6terminal chemical groups as shown in Formula IV, such as 2, 3 or 4terminal chemical groups as shown in Formula IV.

The crosslinker material may comprise a moiety according to Formula V:

wherein R with reference to Formula V comprises the residue of anisocyanurate, biuret, allophonate, glycoluril, benzoguanamine,polyetheramine, and/or polymeric moiety having an Mn of 500 or greater;each R₁ with reference to Formula V is independently a hydrogen, analkyl or a hydroxy functional alkyl having 2 or more carbons and atleast one R₁ with reference to Formula V is a hydroxy functional alkylhaving 2 or more carbons; and n is 2-6.

Suitably, the R₁ group with reference to Formula V may exclude etherlinkages.

The crosslinker may comprise a moiety according to Formula VI:

wherein R₂ with reference to Formula VI comprises a substituted orunsubstituted C₁ to C₃₆ alkyl group, an aromatic group, or the residueof an isocyanurate, biuret, allophonate, glycoluril, benzoguanamine,polyetheramine, and/or a polymeric moiety having an Mn of 500 orgreater; each R₁ with reference to Formula VI is independently ahydrogen, an alkyl group having 1 or more carbons, or a hydroxyfunctional alkyl having 2 or more carbons and at least one R₁ withreference to Formula VI is a hydroxy functional alkyl having 2 or morecarbons; and n is 2-6.

Suitably, when R₂ with reference to Formula VI is a substituted orunsubstituted C₁ to C₃₆ alkyl group the acid functional polyestermaterial comprises COOH functionality that reacts with the polyurea toform an ester linkage.

Suitably, the R₁ group with reference to Formula VI may exclude etherlinkages.

It will be understood that when R₂ with reference to Formula VI is asubstituted or unsubstituted alkyl group, there may be two R₂ groupswith reference to Formula VI attached to the N, and the two R₂ groupswith reference to Formula VI may be the same or different. For example,if the hydroxy functional alkyl polyurea is formed from the reaction ofdimethyl carbonate with dibutylamine and diisopropanol amine, there willbe two R₂ groups with reference to Formula VI that will each be C4.

R and R₂ with reference to Formula VI may comprise the residue of anisocyanurate, biuret, allophonate, glycoluril, benzoguanamine,polyetheramine and/or polymeric moiety having an Mn of 500 or greater.An isocyanurate will be understood as referring to a compound havingthree isocyanate groups, typically in ring form, and is sometimesreferred to as a trimer. This can include compounds having one or moreisocyanurate moieties. Isocyanurates can be purchased from Covestro andVencore X Chemical. Suitable commercially available isocyanuratesinclude those sold under the trade name DESMODUR such as, for example,DESMODUR N 3300A, DESMODUR N3800, DESMODUR N3790, DESMODUR N3400,DESMODUR N3600, DESMODUR N3900 and DESMODUR RC (commercially availablefrom Covestro), those sold under the trade name VESTANANT such as, forexample, VESTANAT T1890/100 (commercially available from Evonik) andthose sold under the trade name EASAQUA such as, for example, EASAQUA WT2102, EASAQUA X D 401, EASAQUA M 501, EASAQUA X D 803, EASAQUA M 502 andEASAQUA X L 600 (commercially available from Vencore X Chemical).Unsaturated isocyanate monomers include but are not limited to2-acryloyloxyethylisocyanate (AOI), 2-methacryloyloxyethyl isocyanate(MOI), alpha, alpha-dimethyl meta-isopropenyl benzyl isocyanate (TMI),and the adduct of 2-hydroxyethyl acrylate (HEA) and IPDI in 1:1 ratio. Aparticularly suitable hydroxy functional alkyl polyurea formed from anisocyanurate is shown in Formula VII:

wherein R₁ with reference to Formula VII is as described above; and eachR₃ independently comprises an alkyl, aryl, alkylaryl, arylalkyl,alicyclic, and/or polyetheralkyl group.

A particularly suitable hydroxy functional alkyl polyurea formed from abis-isocyanurate is shown below in Formula VIII:

wherein R₁ and R₃ with reference to Formula VIII are as described above.

A biuret will be understood as referring to a compound that results uponthe condensation of two molecules of urea, and is sometimes referred toas a carbamylurea. Biurets are commercial available from Vencore XChemical and Covestro as, for example, DESMODUR N-75, DESMODUR N-100,and DESMODUR N-3200, HDB 75B, HDB 75M, HDB 75MX, HDB-LV. A particularlysuitable hydroxy functional alkyl polyurea formed from a biuret is shownbelow in Formula IX:

wherein R₁ with reference to Formula IX is as described above; each R₅independently comprises an alkyl, aryl, alkylaryl, arylalkyl, alicyclic,and/or polyetheralkyl group; and R₆ comprises H or an alkyl group.

Uretidione is a dimer of diisocyanate, examples of which includeDESMODUR N-3400 polyisocyanate, a blend of the trimer and uretidione ofHDI:

wherein each R₅ independently comprises an alkyl, aryl, alkylaryl,arylalkyl, alicyclic, and/or polyetheralkyl group.

An allophonate will be understood as referring to a compound made fromurethane and isocyanate. A method for making an allophonate is describedat Surface Coating, Vol 1, Raw material and their usage, Landon NewYork, Chapman and Hall, Page 106. The reaction is generally depictedbelow in scheme I:

wherein R₅ and R₆ with reference to Scheme I are each as describedabove; and R₇ independently comprises the residue of a primary alcohol.

A glycoluril will be understood as referring to a compound composed oftwo cyclic urea groups joined across the same two-carbon chain, asuitable examples of which includes the below:

Glycoluril is widely commercially available, such as fromSigma-Aldrich.Benzoguanamine is also known as6-phenyl-1,3,5-triazine-2,4-diamine and is commercially available fromThe Chemical Company, Jamestown, R.I.

A polyether amine will be understood as referring to a compound havingone or more amine groups attached to a polyether backbone such as onecharacterized by propylene oxide, ethylene oxide, or mixed propyleneoxide and ethylene oxide repeating units in their respective structures,such as, for example, one of the Jeffamine series products. Examples ofsuch polyetheramines include aminated propoxylated pentaerythritols,such as JEFFAMINE XTJ-616, and those represented by Formulas (X) through(VI).

According to Formula (IV) the polyether amine may comprise:

wherein y=0-39, x+z=1-68.

Suitable amine-containing compounds represented by Formula X include,but are not limited to, amine-terminated polyethylene glycol such asthose commercially available from Huntsman Corporation in its JEFFAMINEED series, such as JEFFAMINE HK-511, JEFFAMINE ED-600, JEFFAMINE ED-900and JEFFAMINE ED-2003, and amine-terminated polypropylene glycol such asin its JEFFAMINE D series, such as JEFFAMINE D-230, JEFFAMINE D-400,JEFFAMINE D-2000 and JEFFAMINE D-4000.

According to Formula XI the polyetheramine may comprise:

wherein each p independently is 2 or 3.

Suitable amine-containing compounds represented by Formula XI include,but are not limited to, amine-terminated polyethylene glycol baseddiamines, such as Huntsman Corporation's JEFFAMINE EDR series, such asJEFFAMINE EDR-148 and JEFFAMINE EDR-176.

According to Formula XII the polyetheramine may comprise:

wherein R₅ is H or C₂H₅, m=0 or 1, a+b+c=5-85.

Suitable amine-containing compounds represented by Formula (VI) include,but are not limited to, amine-terminated propoxylated trimethylolpropaneor glycerol, such as Huntsman Corporation's Jeffamine T series, such asJEFFAMINE T-403, JEFFAMINE T-3000 and JEFFAMINE T-5000.

Particularly suitable are di- and tri-amines, such as4,7,10-trioxa-1,13-tridecanediamine, JEFFAMINE D400, JEFFAMINE D4000,JEFFAMINE D2000, JEFFAMINE T403.

A “polymeric moiety” as used herein in the context of R or R₂ withreference to Formulas V to IX refers to any polymer or oligomer to whichhas been attached two to six hydroxy functional alkyl polyurea groups.The polymer can be, for example, a polyester polyurethane, a polyetherpolyurethane, or a polyamide polyurethane. The moiety can itself containfunctionality, such as acid functionality, hydroxy functionality, and/oramine functionality. The polymeric moiety (which may be oligomeric asnoted above) has an Mn of 500 or greater, such as 1000 or greater, 2500or greater, 4000 or greater, or 5,000 or greater. Mn, as used herein,refers to the number average molecular weight and means the theoreticalvalue as determined by Gel Permeation Chromatography using Waters 2695separation module with a Waters 410 differential refractometer (RIdetector) and polystyrene standards. The Mn values reported according tothe invention were determined using this method. Tetrahydrofuran (THF)was used as the eluent at a flow rate of 1 ml min⁻¹, and two PL GelMixed C columns were used for separation.

In all cases, R and R₂ with reference to Formulas V to IX may besubstituted or unsubstituted. R₂ with reference to Formulas V to IX, asnoted above, may also comprise a substituted or unsubstituted C₁ to C₃₆alkyl group and/or an aromatic group. For example, the alkyl group mayhave two to ten carbon atoms, such as six carbon atoms. The alkyl groupmay derive from an isocyanate, such as a diisocyanate. Suitable examplesinclude isophorone diisocyanate and hexamethylene isocyanate. Thearomatic group may derive from an aromatic ring containing isocyanate,suitable examples of which include methylene diphenyl diisocyanate,toluene diisocyanate and tetramethylxylylene diisocyanate.

Certain hydroxy functional alkyl polyureas of, and/or used according to,the invention may be made by reacting an isocyanate-containing compoundwith amino alcohol. Any isocyanate-containing compound having at leasttwo isocyanate groups can be used, such as any of those described above.It will be appreciated that the “R” or “R₂” group with reference toFormulas V to IX will reflect the isocyanate-containing compoundselected, if one is used.

Similarly, any amino alcohol having two or more carbon atoms can beused, and the “R₁” group with reference to Formulas V to IX will reflectthe amino alcohol selected. The amino alcohol can have one, two or morehydroxyl functional groups. One or more amino alcohols can be used,which will result in different R₁ groups with reference to Formulas V toIX being present on the polyurea. R₁ with reference to Formulas V to IXcan also be hydrogen or an alkyl group. Suitable amino alcohols includemonoethanol amine, diethanol amine and diisopropanol amine.

The hydroxyl functional alkyl polyureas can be made by reacting aminoalcohol with an isocyanate-containing compound in an organic polarsolvent, such as alcohol or water. The equivalent ratio of amine toisocyanate may be 2-1:1-2, such as 1:1.

The hydroxy functional alkyl polyureas may be made by alternativemethods as well. For example, amino alcohols can react with carbonate toform hydroxylalkyl carbamate, and hydroxylalkyl carbamate can furtherreact with amines to form hydroxy functional alkyl polyureas.

The number-average molecular weight (Mn) of the hydroxy functional alkylpolyurea (even when the polyurea is in the form of a monomer orprepolymer, but not when R or R2 with reference to Formulas V to IX is apolymeric moiety) may be 100 or greater, such as 350 or greater or 1,000or greater, and/or can be 6,000 or lower, such as 3,000 or lower, or2,000 or lower. The Mn of the hydroxy functional alkyl polyurea when Ror R₂ with reference to Formulas V to IX is a polymeric moiety can be500 or greater, such as 1,000 or greater, 5,000 or greater or 10,000 orgreater.

It has surprisingly and advantageously been found by the presentinventors that the hydroxyl alkyl urea functional materials typicallycure at a lower temperature than, for example, hydroxyalkylamidematerial, such as a β-hydroxyalkylamide material.

The crosslinker may be in the form of a carbodiimide resin. Thecrosslinker may comprise a polycarbodiimide. Suitably, the crosslinkermay comprise a polycarbodiimide having the following structural units(XIII) or (XIV) including mixtures thereof:

where e is an integer of from 2 to 20; f and g are each at least 1, andf+g is an integer up to 20;

E is a radical selected from

where R² with reference to structural units (XIII) or (XIV) comprises acyclic radical and R³ with reference to (XV) and (XVI) is a linearhydrocarbon radical containing at least 4 carbon atoms and R⁴ withreference to (XVI)is hydrogen or an alkyl radical.

The polycarbodiimides may be prepared by reacting an organic groupcontaining a polyisocyanate in the presence of a suitable catalyst toform a polycarbodiimide having terminal NCO-functionality, wherein anactive hydrogen-containing compound is added before, during or afterpolycarbodiimide formation.

The polyisocyanate can be an aliphatic, including cycloaliphatic, or anaromatic polyisocyanate or mixture of the two. Aliphatic includingcycloaliphatic polyisocyanates and alkaryl polyisocyanates areparticularly suitable. The polyisocyanates can contain from 2 to 4, suchas 2 isocyanate groups per molecule. Examples of suitable higherpolyisocyanates are 1,2,4-benzene triisocyanate and polymethylenepolyphenyl isocyanate. Examples of suitable aromatic diisocyanates are4,4′-diphenylmethane diisocyanate, 1,3-phenylene diisocyanate,1,4-phenylene diisocyanate and tolylene diisocyanate. Examples ofsuitable aliphatic diisocyanates are straight chain aliphaticdiisocyanates such as 1,4-tetramethylene diisocyanate and1,6-hexamethylene diisocyanate and alkaryl polyisocyanates such asm-tetramethylxylene diisocyanate. Also, cycloaliphatic diisocyanates canbe employed. Examples include 1,4-cyclohexyl diisocyanate, isophoronediisocyanate, alpha, alpha-xylylene diisocyanate and4,4-methylene-bis(cyclohexyl isocyanate). Substituted organicgroup-containing polyisocyanates can also be used in which thesubstituents are nitro, chloro, alkoxy and other groups that are notreactive with hydroxyl groups or active hydrogens and provided thesubstituents are not positioned to render the isocyanate groupunreactive.

The active hydrogen-containing compound used in the preparation of thepolycarbodiimide is suitably a chain extender or spacer linkingpolyisocyanates together to form NCO-adducts or to link NCO-functionalpolycarbodiimides together. Any suitable organic compound containingactive hydrogens may be used. The term “active hydrogen atoms” refers tohydrogens which, because of their position in the molecule, displayactivity according to the Zerewitinoff test. Accordingly, activehydrogens include hydrogen atoms attached to oxygen or nitrogen, andthus useful compounds will include those having at least two of thesegroups (in any combination):

-   -   —OH, and —NH₂

The moieties attached to each group can be aliphatic, includingcycloaliphatic, aromatic, or of a mixed type with aliphatic beingparticularly suitable.

The active hydrogen-containing material can contain from 2 to 4,particularly suitable 2 active hydrogens per molecule.

Examples of such compounds include amines, which includes polyamines,aminoalcohols, mercapto-terminated derivatives, and alcohols thatincludes polyhydroxy materials (polyols) that are particularly suitablebecause of the ease of reaction with polyisocyanates. Also polyolsgenerally give no side reactions, giving higher yields of urethaneproduct with no by-product and the products are hydrolytically stable.Also, with regard to polyols, there are a wide variety of materialsavailable which can be selected to give a wide spectrum of desiredproperties. In addition, the polyols have desirable reaction rates withpolyisocyanates. Both saturated and unsaturated activehydrogen-containing compounds can be used, but saturated materials areparticularly suitable because of superior coating properties.

The polyhydroxyl materials or polyols can be either low or highmolecular weight materials and in general will have average hydroxylvalues as determined by ASTM designation E-222-67, Method B, of 2000 andbelow, such as between 2000 and 10. The term “polyol” is meant toinclude materials having an average of two or more hydroxyl groups permolecule.

The polyols include low molecular weight diols, triols and highermolecular weight polyols, low molecular weight amide-containing polyolsand higher polymeric polyols such as polyester polyols, polyetherpolyols, polycarbonate polyols and hydroxy-containing (meth)acrylicpolymers. The polymers typically have hydroxyl values of from 10 to 180.Also, the polymers typically have number average molecular weights of 96to 10,000 Da.

The low molecular weight diols, triols and higher alcohols useful in theinstant invention are known in the art. They have hydroxy values of 200or above, usually within the range of 200 to 2000. Such materialsinclude aliphatic polyols, particularly alkylene polyols containing from4 to 18 carbon atoms. Examples include 1,4-butanediol and1,6-hexanediol. Also useful are polyols containing ether linkages suchas diethylene glycol and tetraethylene glycol.

To form the polycarbodiimide, the polyisocyanate with or without theactive hydrogen-containing compound may be condensed with theelimination of carbon dioxide to form the polycarbodiimide, that is, apolymer containing [N═C═N]_(n) units where n with reference to the[N═C═N]=2 to 20, such as 2 to 10.

The condensation reaction is typically conducted by taking the solutionof the polyisocyanate and heating in the presence of suitable catalyst.Examples of catalyst include 1-ethyl-3-phospholine,1-ethyl-3-methyl-3-phospholine-1-oxide,1-ethyl-3-methyl-3-phospholine-1-sulfide,1-ethyl-3-methyl-phospholidine, 1-ethyl-3-methyl-phospholidine-1-oxide,3-methyl-1-phenyl-3-phospholine-1-oxide and bicyclic terpene alkyl orhydrocarbyl aryl phosphine oxide or camphene phenyl phosphine oxide.

The particular amount of catalyst used will depend to a large extent onthe reactivity of the catalyst itself and the polyisocyanate being used.A concentration range of 0.05-5 parts of catalyst per 100 parts ofadduct is generally suitable.

The resulting polycarbodiimide has terminal NCO groups that can then bereacted with an active hydrogen-containing hydrophilic compound.

The hydrophilic compound may be a polyether alcohol or polyether amineor mixtures thereof having a polyether backbone, typically based onethylene oxide or mixed ethylene oxide and propylene and having amolecular weight greater than 500, such as at least 1000 on a numberaverage basis. Typical alcohols and amines have the following structuralformula:

R—(—O—CH₂—CH₂—)_(a)—(—O—CH₂—CH(CH₃)-)_(b)-D-N(R¹)—H   (XVII)

or

R—(—O—CH₂—CH₂—)_(a)—(—O—CH₂—CH(CH₃)-)_(b)-D-OH   (XVIII)

where R with reference to formulas (XVII) and (XVIII) is C₁ to C₄ alkyl;a with reference to formulas (XVII) and (XVIII) is 5 to 50 and b withreference to formulas (XVII) and (XVIII) is 0 to 35, and when b withreference to formulas (XVII) and (XVIII) is present the mole ratio of ato b with reference to formulas (XVII) and (XVIII) is at least 1:1; R¹with reference to formula (XVIII) is hydrogen or a hydrocarbon radicaland D with reference to formulas (XVII) and (XVIII) is a divalentlinking group or a chemical bond.

Reaction of the polyether alcohol or amine with the NCO-containingcarbodiimide may be conducted with a stoichiometric equivalent of amineto NCO equivalents or a slight excess of alcohol or amine and at atemperature typically from 80 to 110° C. until an IR spectrum of thereaction mixture indicates substantially no remaining NCO functionality.

Depending on when the active hydrogen chain extender or spacer is usedin the reaction, the polycarbodiimide has a structure such that eachcarbodiimide unit or polycarbodiimide unit is attached to a unitselected from urethane, thiourethane urea, thiourea and a hydrophilicunit occurs at one or terminal positions of the polycarbodiimide via aurethane or urea linkage.

Typically, the polycarbodiimide has a weight average molecular weight of2600 to 12,000, such as 3000 to 10,000, and a diimide equivalent weight(number average molecular weight/number of carbodiimide groups) of atleast 600, such as 600 to 2000.

When the active hydrogen chain extender is added before or duringpolycarbodiimide formation, that is, is used to chain extend apolyisocyanate to form an NCO-adduct, the polycarbodiimide can berepresented from the following structural formula when thepolyisocyanate and the active hydrogen-containing compound aredifunctional:

where e with reference to formula (XIX) is an integer of from 2 to 20,such as 2 to 10; E with reference to formula (XIX) is a radical selectedfrom

where R² with reference to formula (XIX) is a cyclic radical such as acycloaliphatic or an alkaryl radical that may contain 6 to 20 carbonatoms such as those of the structure:

R³ with reference to formula (XX) and (XXI) is a linear hydrocarbonradical optionally including hetero atoms containing at least 4 carbonatoms such as a polyethylene group having a number average molecularweight of 96 to 10,000. R⁴ with reference to formula (XXI) is hydrogenor a hydrocarbon radical such as alkyl containing from 1 to 4 carbonatoms. Y with reference to formula (XIX) is a radical of the structure:

R—(—O—CH₂—CH₂—)_(a)—(—O—CH₂—CH(CH₃)-)_(b)-D-N(R¹)—C(O)—NH—  (XXII)

or

R—(—O—CH₂—CH₂—)_(a)—(—O—CH₂—CH(CH₃)-)_(b)-D-O—C(O)—NH—  (XXIII)

where R with reference to formula (XXII) and (XXIII) is C₁ to C₄ alkyl;a with reference to formula (XXII) and (XXIII) is 5 to 50 and b withreference to formula (XXII) and (XXIII) is 0 to 35, and when b withreference to formulas (XXII) and (XXIII) is present the mole ratio of ato b with reference to formulas (XXII) and (XXIII) is at least 1:1; R¹with reference to formula (XXII) is hydrogen or a hydrocarbon radicaland D with reference to formula (XXII) and (XXIII) is a divalent linkinggroup or a chemical bond.

When the active hydrogen chain extender is added after polycarbodiimideformation, that is, is used to chain extend an NCO-functionalpolycarbodiimide, the polycarbodiimide can be represented from thefollowing structural formula when the NCO-functional polycarbodiimideand the active hydrogen-containing compound are difunctional.

where f and g with reference to formula (XXIV) are each at least 1, andf+g with reference to formula (XXIV) is an integer up to 20 such as upto 10; E with reference to formula (XXIV) is a radical selected from

where R², R³, R⁴ and Y with reference to formulas (XXIV), (XXV) and(XXVI) have the meanings mentioned above for (XIX).

Organic solvent can optionally be present in the synthesis of thepolycarbodiimide. Polar water miscible solvents such as N-methylpyrrolidone can be used in amounts of about 5-25 percent by weight basedon weight of the reaction mixture.

The powder coating composition may comprise any suitable weight ratio ofacid functional polyester material (a) to crosslinker (b). The powdercoating composition may have a weight ratio of (a) to (b) from to 50:1to 1:1, suitably from 25:1 to 1:1, such as from 20:1 to 5:1, or evenfrom 15:1 to 5:1. Suitably, the powder coating composition may have aweight ratio of (a) to (b) of 10:1.

The powder coating composition of the present invention may have anysuitable average particle size (D₅₀). The powder coating composition mayhave an average particle size from 5 to 300 microns (μm), suitably from5 to 150 μm, such as from 10 to 75 μm, or even from 10 to 50 μm.Particles having these sizes may be produced by any suitable method.Suitable methods will be well known to a person skilled in the art.Examples of suitable methods include, but are not limited to, coldgrinding and sieving methods.

The average particle size (D₅₀) may be measured by any suitable method.Suitable methods will be well known to a person skilled in the art. Theaverage particle size (D₅₀) may be measured using laser diffractionanalysis. Suitably, the laser diffraction analysis may be performedusing a Microtrac S3000 laser diffraction analyser (commerciallyavailable from Microtrac), suitably according to the manufacturer'sprotocol. All values for average particle size (D₅₀) reported hereinwere measured this way.

The powder coating compositions of the present invention may compriseany suitable amount of thermoset resin. The powder coating compositionmay comprise from 1 to 90 wt %, suitably from 2 to 70 wt %, such as from5 to 50 wt %, of the thermoset resin based on the total solid weight ofthe coating composition.

The thermoset resin may comprise any suitable amount of acid functionalpolyester material. The thermoset resin may comprise up to 50 wt %,suitably up to 75 wt %, such as up to 90 wt % or even up to 100 wt %acid functional polyester material based on the total solid weight ofthe thermoset resin.

The powder coating compositions of the present invention may compriseany suitable amount of acid functional polyester material. The powdercoating composition may comprise from 1 to 90 wt %, suitably from 2 to70 wt %, such as from 5 to 50 wt % of the acid functional polyestermaterial based on the total solid weight of the coating composition.

The powder coating compositions of the present invention may compriseany suitable amount of thermoplastic resin. The powder coatingcomposition may comprise from 1 to 90 wt %, suitably from 10 to 80 wt %,such as from 10 to 75 wt %, or even from 20 to 50 wt % of the acidfunctional polyester material based on the total solid weight of thecoating composition.

The powder coating compositions may comprise any suitable amount ofcrosslinker. The powder coating compositions may comprise from 0.5 to 50wt %, suitably from 1 to 40 wt %, such as from 2 to 30 wt %, or evenfrom 5 to 20 wt % of the crosslinker based on the total solid weight ofthe coating composition. Suitably, the powder coating compositions maycomprise from 5 to 10 wt % of the crosslinker based on the total solidweight of the coating composition.

The powder coating compositions may comprise less than 7 wt %, suitablyless than 6 wt % of the crosslinker based on the total solid weight ofthe coating composition. The powder coating compositions may comprisefrom 0.5 to 7 wt %, suitably from 1 to 7 wt %, such as from 2 to 7 wt %,or even from 5 to 7 wt % of the crosslinker based on the total solidweight of the coating composition. The powder coating compositions maycomprise from 0.5 to 6 wt %, suitably from 1 to 6 wt %, such as from 2to 6 wt %, or even from 5 to 6 wt % of the crosslinker based on thetotal solid weight of the coating composition.

Suitably, the powder coating compositions may comprise less than 6 wt %of the crosslinker based on the total solid weight of the coatingcomposition.

It has surprisingly and advantageously been found by the presentinventors that a lower amount of crosslinker may be used in the powdercoating compositions of the present invention compared to the amountsthat are typically used in powders of the prior art. In particular, ithas surprisingly and advantageously been found by the present inventorsthat a lower amount of β-hydroxyalkylamide material may be used in thepowder coating compositions of the present invention compared to theamounts that are typically used in powders of the prior art.

The powder coating compositions may further comprise one or more pigmentand/or filler. The powder coating composition may comprise a singlepigment or filler or a mixture of pigments and/or fillers. Suitablepigments include, but are not limited to, the following: titaniumdioxide; ultramarine blue; phthalocyanines, such as phthalocyanine blueand phthalocyanine green; anthraquinones; quinacridones; thioindigos;carbon black; graphite fibrils; iron oxides, such as black iron oxide;chromium green oxide; ferried yellow; quindo red; or combinationsthereof.

Suitable fillers include, but are not limited to, the following: bariumsulphate; silicas, such as precipitated silicas and clay; orcombinations thereof.

Suitably, the powder coating composition may comprise titanium dioxide,barium sulphate or a combination thereof. Suitably, the powder coatingcomposition may comprise titanium dioxide and barium sulphate.

The pigment and/or filler, when present, may be used in the powdercoating compositions in any suitable amount. The pigment and/or filler,when present, may be used in the powder coating composition in amountsof at least 10 wt % based on the total solid weight of the coatingcomposition. The powder coating composition may comprise from 10 to 90wt %, suitably from 10 to 80 wt %, such as from 10 to 70 wt %, or evenfrom 10 to 50 wt % of pigment and/or filler based on the total solidweight of the powder coating composition. The powder coating compositionmay comprise from 15 to 90 wt %, suitably from 15 to 80 wt %, such asfrom 15 to 70 wt %, or even from 15 to 50 wt % of pigment and/or fillerbased on the total solid weight of the coating composition. The powdercoating composition may comprise from 20 to 90 wt %, suitably from 20 to80 wt %, such as from 20 to 70 wt %, or even from 20 to 50 wt % ofpigment and/or filler based on the total solid weight of the powdercoating composition.

The powder coating composition may further comprise one or more curingcatalyst. The powder coating compositions may comprise any curing agentsuitable to catalyse the reaction between the acid functional polyestermaterial and the β-hydroxyalkylamide crosslinker. Suitable curingcatalysts will be well known to a person skilled in the art. Examples ofsuitable curing catalysts include, but are not limited to, thefollowing: organic tin compounds, such as tin (II) salts of carboxylicacids, for example, tin (II) acetate, tin (II) octonoate, tin (II)ethylhexanoate and tin (II) laurate, tin (IV) compounds, for example,dibutyltin oxide, dibutyltin dichloride, dibutyltin diacetate,dibutyltin dilaurate, dibutyltin maleate and dioctyltin diacetate;tertiary amines, such as diazabicyclo[2.2.2]octane and1,5-diazabicyclo[4.3.0]non-5-ene; and combinations thereof.

The powder coating compositions of the present invention may optionallycomprise a further additive or combination of additives. The powdercoating composition may optionally comprise any suitable additive orcombination of additives. Suitable additives will be well known to theperson skilled in the art. Examples of suitable additives include, butare not limited to the following: lubricants; diluents; plasticisers;surfactants; stabilising agents; flow control agents; thixotropicagents; and combinations thereof.

Suitable lubricants will be well known to the person skilled in the art.Suitable examples of lubricants include, but are not limited to one ormore of the following: carnauba wax and polyethylene type lubricants.The lubricant, when present, may be used in the thermoset powder coatingcomposition in amounts of at least 0.01 wt % based on the total solidweight of the powder coating composition.

Surfactants may optionally be added to the powder coating composition inorder to aid in flow and wetting of the substrate. Suitable surfactantswill be well known to the person skilled in the art. It will beappreciated by a person skilled in the art that when the thermosetpowder coating composition is to be used in food and/or beveragecontainer applications, the surfactant, when present, is chosen to becompatible with such applications. Suitable surfactants include, but arenot limited to one or more of the following: alkyl sulphates (e.g.,sodium lauryl sulphate); ether sulphates; phosphate esters; sulphonates;and their various alkali, ammonium, amine salts; aliphatic alcoholethoxylates; alkyl phenol ethoxylates (e.g. nonyl phenol polyether);salts and/or combinations thereof. The surfactants, when present, may bepresent in amounts from 0.01 to 10 wt % based on the total solid weightof the powder coating composition.

Suitable flow control agents will be well known to a person skilled inthe art. Suitable flow control agents include, but are not limited to,the following: acrylate polymers, such as polylauryl acrylate, polybutylacrylate, poly(2-ethylhexyl) acrylate, poly(ethyl-2-ethylhexyl)acrylate, polylauryl methacrylate and polyisodecenyl methacrylate;fluorinated polymers, such as an ester of polyethylene glycol orpolypropylene glycol and fluorinated fatty acids, for example, an esterof polyethylene glycol of a molecular weight of over 2,500 Da andperfluorooctanoic acid; polymeric siloxanes, such as polymeric siloxanesof a molecular weight of over 1,000 Da, for example,poly(dimethylsiloxane) and poly(methylphenylsiloxane); and combinationsthereof. The flow control agents, when present, may be present inamounts from 0.01 to 10 wt %, suitably from 0.1 to 5 wt %, such as from0.5 to 4 wt %, or even from 1 to 3 wt % based on the total solid weightof the powder coating composition. It will be appreciated by a personskilled in the art that the flow controls agents, when present, must besuitable for use in a powder composition.

The powder coating compositions according to the present invention aresubstantially free of bisphenol A (BPA) and derivatives thereof. Thepowder coating compositions may be essentially free or may be completelyfree of bisphenol A (BPA) and derivatives thereof. Derivatives ofbisphenol A include, for example, bisphenol A diglycidyl ether (BADGE).The powder coating compositions according to the present invention arealso substantially free of bisphenol F (BBF) and derivatives thereof.The powder coating compositions may be essentially free or may becompletely free of bisphenol F (BPF) and derivatives thereof.Derivatives of bisphenol F include, for example, bisphenol F diglycidylether (BPFG). The compounds or derivatives thereof mentioned above maynot be added to the composition intentionally but may be present intrace amounts because of unavoidable contamination from the environment.“Substantially free” refers to powder coating compositions, orcomponents thereof, containing less than 1000 parts per million (ppm) ofany of the compounds or derivatives thereof mentioned above.“Essentially free” refers to powder coating compositions, or componentsthereof, containing less than 100 ppm of any of the compounds orderivatives thereof mentioned above. “Completely free” refers to powdercoating compositions, or components thereof, containing less than 20parts per billion (ppb) of any of the compounds or derivatives thereofmentioned above.

The powder coating compositions of the present invention may besubstantially free, may be essentially fee or may be completely free ofdialkyltin compounds, including oxides or other derivatives thereof.Examples of dialkyltin compounds include, but are not limited to one ormore of the following: dibutyltindilaurate (DBTDL); dioctyltindilaurate;dimethyltin oxide; diethyltin oxide; dipropyltin oxide; dibutyltin oxide(DBTO); dioctyltinoxide (DOTO) or combinations thereof. “Substantiallyfree” refers to powder coating compositions, or components thereof,containing less than 1000 parts per million (ppm) of any of thecompounds or derivatives thereof mentioned above. “Essentially free”refers to powder coating compositions, or components thereof, containingless than 100 ppm of any of the compounds or derivatives thereofmentioned above. “Completely free” refers to powder coatingcompositions, or components thereof, containing less than 20 parts perbillion (ppb) of any of the compounds or derivatives thereof mentionedabove.

The powder coating compositions of the present invention may besubstantially free, may be essentially fee or may be completely free offormaldehyde or sources thereof. “Substantially free” refers to powdercoating compositions, or components thereof, containing less than 1000parts per million (ppm) formaldehyde or sources thereof mentioned above.“Essentially free” refers to powder coating compositions, or componentsthereof, containing less than 100 ppm formaldehyde or sources thereofmentioned above. “Completely free” refers to powder coatingcompositions, or components thereof, containing less than 20 parts perbillion (ppb) formaldehyde or sources thereof.

It will be appreciated by a person skilled in the art that thecrosslinking material, when present, may be selected so as to besubstantially free, essentially fee or completely free of formaldehydeor sources thereof.

The powder coating compositions of the present invention may besubstantially free, may be essentially free or may be completely free ofbromine. “Substantially free” refers to powder coating compositions, orcomponents thereof, containing less than 1000 parts per million (ppm) ofbromine. “Essentially free” refers to powder coating compositions, orcomponents thereof, containing less than 100 ppm of bromine. “Completelyfree” refers to powder coating compositions, or components thereof,containing less than 20 parts per billion (ppb) of bromine.

The powder coating compositions of the present invention may besubstantially free, may be essentially free or may be completely free ofsolvent. “Substantially free” refers to powder coating compositions, orcomponents thereof, containing less than 1000 parts per million (ppm) ofsolvent. “Essentially free” refers to powder coating compositions, orcomponents thereof, containing less than 100 ppm of solvent. “Completelyfree” refers to powder coating compositions, or components thereof,containing less than 20 parts per billion (ppb) of solvent.

The powder coating composition of the present invention may be preparedby any suitable method. For example, the powder coating composition maybe prepared by first dry blending the thermoset resin comprising an acidfunctional polyester material, the thermoplastic resin, the crosslinkermaterial and, if present, pigment and/or filler, curing agent andadditives in a blender. The blender may be operated for any suitableperiod of time. Suitably, the blender may be operated for a period oftime sufficient to result in a homogeneous dry blend of the materialscharged thereto. The homogenous dry blend may then be melt blended in anextruder, such as a twin-screw co-rotating extruder, operated within atemperature range from 80 to 140° C., suitably from 100 to 125° C. Theextrudate of the thermoset powder may be cooled and is typically milledto an average particle size as described above.

The powder coating composition may be prepared by first dispersing thethermoset resin comprising an acid functional polyester material (a),the thermoplastic resin (b), crosslinker material (c) and, if present,pigment and/or filler and additives in a liquid carrier. The dispersionmay then be dried to form a powder. The dispersion may be dried to apowder by any suitable method, such as spray drying, drying on heatedplates, microwave drying, drum drying or any know method of evaporationtechniques. The dried powder may then be ground or milled to an averageparticle size as described above.

Thus, according to a second aspect of the present invention there isprovided a method for producing a powder coating composition comprising:

-   -   a) a thermoset resin comprising an acid functional polyester        material,    -   b) a thermoplastic resin and    -   c) a crosslinker material,        the method comprising the steps of:    -   i) dispersing components (a), (b) and (c) in a liquid carrier,    -   ii) drying the dispersion of step (i) to form a powder, and    -   iii) grinding the powder of step (ii) to a particle size of 5 to        300 micron (μm),        wherein the coating composition is substantially free of        bisphenol A (BPA), bisphenol F (BPF), bisphenol A diglycidyl        ether (BADGE) and bisphenol F diglycidyl ether (BFDGE).

The liquid carrier may comprise water, an organic solvent, a mixture ofwater and one or more organic solvent(s) or a mixture of organicsolvents. Suitably, the liquid carrier may comprise water. The liquidcarrier may be present in the form of a dispersion of the thermoplasticresin as described above.

Suitable organic solvents include, but are not limited to one or more ofthe following: aliphatic hydrocarbons such as mineral spirits and highflash point naphtha; aromatic hydrocarbons such as benzene; toluene;xylene; solvent naphtha 100, 150, 200; those available from Exxon-MobilChemical Company under the SOLVESSO trade name; alcohols such asethanol; n-propanol; isopropanol; and n-butanol; ketones such asacetone; cyclohexanone; methylisobutyl ketone; methyl ethyl ketone;esters such as ethyl acetate; butyl acetate; n-hexyl acetate; glycolssuch as butyl glycol; glycol ethers such as methoxypropanol; ethyleneglycol monomethyl ether; ethylene glycol monobutyl ether andcombinations thereof

It will be appreciated by a person skilled in the art that, when thethermoplastic resin is provided in the form of a dispersion, some or allof the liquid carrier of step (i) of the second aspect of the presentinvention may be present in the form of the liquid carrier of thethermoplastic resin dispersion.

It will be appreciated by a person skilled in the art that when thecrosslinker material is provided in the form of a dispersion, some orall of the liquid carrier of step (i) of the second aspect of thepresent invention may be present in the form of the liquid carrier ofthe crosslinker material dispersion. For example, when the crosslinkermaterial is a polycarbodiimide material and is provided in the form of adispersion, some or all of the liquid carrier of step (i) of the secondaspect of the present invention may be present in the form of the liquidcarrier of the crosslinker material dispersion.

It has surprisingly and advantageously found by the present inventorsthat the method according to the second aspect of the present inventionenables both thermosetting and thermoplastic resins to be included in acoating composition. Typically, these two types of resins areincompatible, as would be well known to a person skilled in the art.

The powder coating composition of the present invention is a curablecoating composition. “Curable coating compositions” and like terms asused herein, refers to coating compositions that have an initial powderstate and a final state in which the coating composition has beentransformed into a substantially continuous, coalesced state.

The powder coating composition of the present invention may be cured byany suitable method. The powder coating composition may be cured by heatcuring or by chemical curing, suitably by heat curing. The powdercoating composition, when heat cured, may be cured at any suitabletemperature. The powder coating composition, when heat cured, may becured at temperatures from 50 to 350° C., suitably from 100 to 320° C.,such as from 150 to 300° C., or even from 200 to 300° C.

The powder coating composition according to the first aspect of thepresent invention may be applied to any suitable substrate. The powdercoating composition may be applied to a metal substrate. Examples ofsuitable metal substrates include, but are not limited to, food and/orbeverage packaging, components used to fabricate such packaging ormonobloc aerosol cans and/or tubes. Suitably, the food and/or beveragepackaging may be a can. Examples of cans include, but are not limited toone or more of the following, two-piece cans, three-piece cans and thelike. Suitable examples of monobloc aerosol cans and/or tubes include,but are not limited to, deodorant and hair spray containers. Monoblocaerosol cans and/or tubes may be aluminium monobloc aerosol cans and/ortubes.

The powder coating compositions may be applied to food and/or beveragepackaging or components used to fabricate such packaging.

The powder coating compositions may be applied to monobloc aerosol cansand/or tubes.

The application of various pre-treatments and coatings to packaging iswell established. Such treatments and/or coatings, for example, can beused in the case of metal cans, wherein the treatment and/or coating isused to retard or inhibit corrosion, provide a decorative coating,provide ease of handling during the manufacturing process, and the like.Coatings can be applied to the interior of such cans to prevent thecontents from contacting the metal of the container. Contact between themetal and a food or beverage, for example, can lead to corrosion of ametal container, which can then contaminate the food or beverage. Thisis particularly true when the contents of the can are acidic in nature.The coatings applied to the interior of metal cans also help preventcorrosion in the headspace of the cans, which is the area between thefill line of the product and the can lid; corrosion in the headspace isparticularly problematic with food products having a high salt content.Coatings can also be applied to the exterior of metal cans. Certainpowder coatings of the present invention are particularly applicable foruse with coiled metal stock, such as the coiled metal stock from whichthe ends of cans are made (“can end stock”), and end caps and closuresare made (“cap/closure stock”). Since coatings designed for use on canend stock and cap/closure stock are typically applied prior to the piecebeing cut and stamped out of the coiled metal stock, they are typicallyflexible and extensible. For example, such stock is typically coated onboth sides. Thereafter, the coated metal stock is punched. For can ends,the metal is then scored for the “pop-top” opening and the pop-top ringis then attached with a pin that is separately fabricated. The end isthen attached to the can body by an edge rolling process. A similarprocedure is done for “easy open” can ends. For easy open can ends, ascore substantially around the perimeter of the lid allows for easyopening or removing of the lid from the can, typically by means of apull tab. For caps and closures, the cap/closure stock is typicallycoated, such as by roll coating, and the cap or closure stamped out ofthe stock; it is possible, however, to coat the cap/closure afterformation. Coatings for cans subjected to relatively stringenttemperature and/or pressure requirements should also be resistant topopping, corrosion, blushing and/or blistering.

Accordingly, the present invention is further directed to a packagecoated at least in part with any of the powder coating compositionsdescribed above. A “package” is anything used to contain another item,particularly for shipping from a point of manufacture to a consumer, andfor subsequent storage by a consumer. A package will be thereforeunderstood as something that is sealed so as to keep its contents freefrom deterioration until opened by a consumer. The manufacturer willoften identify the length of time during which the food or beverage willbe free from spoilage, which typically ranges from several months toyears. Thus, the present “package” is distinguished from a storagecontainer or bakeware in which a consumer might make and/or store food;such a container would only maintain the freshness or integrity of thefood item for a relatively short period. A package according to thepresent invention can be made of metal or non-metal, for example,plastic or laminate, and be in any form. An example of a suitablepackage is a laminate tube. Another example of a suitable package ismetal can. The term “metal can” includes any type of metal can,container or any type of receptacle or portion thereof that is sealed bythe food and/or beverage manufacturer to minimize or eliminate spoilageof the contents until such package is opened by the consumer. Oneexample of a metal can is a food can; the term “food can(s)” is usedherein to refer to cans, containers or any type of receptacle or portionthereof used to hold any type of food and/or beverage. The term “metalcan(s)” specifically includes food cans and also specifically includes“can ends” including “E-Z open ends”, which are typically stamped fromcan end stock and used in conjunction with the packaging of food andbeverages. The term “metal cans” also specifically includes metal capsand/or closures such as bottle caps, screw top caps and lids of anysize, lug caps, and the like. The metal cans can be used to hold otheritems as well, including, but not limited to, personal care products,bug spray, spray paint, and any other compound suitable for packaging inan aerosol can. The cans can include “two piece cans” and “three-piececans” as well as drawn and ironed one-piece cans; such one piece cansoften find application with aerosol products. Packages coated accordingto the present invention can also include plastic bottles, plastictubes, laminates and flexible packaging, such as those made from PE, PP,PET and the like. Such packaging could hold, for example, food,toothpaste, personal care products and the like.

The powder coating can be applied to the interior and/or the exterior ofthe package. The powder coating could also be applied as a rim coat tothe bottom of the can. The rim coat functions to reduce friction forimproved handling during the continued fabrication and/or processing ofthe can. The powder coating can also be applied to caps and/or closures;such application can include, for example, a protective varnish that isapplied before and/or after formation of the cap/closure and/or apigmented enamel post applied to the cap, particularly those having ascored seam at the bottom of the cap. Decorated can stock can also bepartially coated externally with the coating described herein, and thedecorated, coated can stock used to form various metal cans.

Metal coils, having wide application in many industries, are alsosubstrates that can be coated according to the present invention. Coilcoatings also typically comprise a colorant.

The powder coating composition according to the first aspect of thepresent invention may be applied to at least a portion of the metalsubstrate. For example, when the powder coating composition is appliedto a monobloc aerosol tube and/or can, the powder coating compositionmay be applied to at least a portion of an internal surface of said tubeand/or can.

The powder coating compositions according to the first aspect of thepresent invention may be applied to the metal substrate by any suitablemethod. Methods of applying said powder coating compositions to themetal substrate will be well known to a person skilled in the art.Suitable application methods include, but are not limited to one or moreof the following: spray coating; roll coating; dipping; andelectrocoating such as, for example, ultra corona discharge. Suitably,the powder coating compositions according to the present invention maybe applied to the monobloc aerosol can by ultra corona discharge.

When the substrate is electrically conductive, the powder coatingcomposition is typically electrostatically applied. Electrostatic sprayapplication generally involves drawing the powder coating compositionfrom a fluidized bed and propelling it through a corona field. Theparticles of the powder coating composition become charged as they passthrough the corona field and are attracted to and deposited upon theelectrically conductive substrate, which is grounded. As the chargedparticles begin to build up, the substrate becomes insulated, thuslimiting further particle deposition. This insulating phenomenontypically limits the film build of the deposited coating composition toa maximum of 250 to 300 μm (microns), in some cases, 75 to 150 μm.

The powder coating compositions according to the present invention maybe applied to the metal substrate to any suitable dry film thickness.The powder coating compositions according to the first aspect of thepresent invention may be applied to the metal substrate to a dry filmthickness from 0.1 μm (microns) to 300 μm, suitably from 3 μm to 250 μm,such as from 5 μm to 150 μm, or even from 5 μm to 75 μm, such as from 10μm to 25 μm.

The powder coating composition according to the present invention may beapplied to the metal substrate as a single layer or as part of a multilayer system. The powder coating compositions according to the firstaspect of the present invention may be applied to the metal substrate asa single layer. The powder coating compositions according to the firstaspect of the present invention may be applied to the metal substrate asthe first coat of a multi coat system. Suitably, the powder coatingcompositions according to the first aspect of the present may be appliedto the metal substrate as an undercoat or a primer. The second, third,fourth etc. coats may comprise any suitable paint such as thosecontaining, for example, epoxy resins; polyester resins; polyurethaneresins; polysiloxane resins; hydrocarbon resins or combinations thereof.The powder coating compositions according to the first aspect of thepresent invention may be applied on top of another paint layer as partof a multi layer system. For example, the powder coating compositions ofthe first aspect of the present invention may be applied on top of aprimer. The powder coating compositions according to the first aspect ofthe present invention may form an intermediate layer or a top coatlayer. The powder coating compositions according to the presentinvention may be applied to the metal substrate once or multiple times.Any or all of the layers may be substantially free, essentially free orcompletely free of BPA, BPF and derivatives thereof.

According to a further aspect of the present invention there is provideda metal substrate coated on at least a portion thereof with a powdercoating composition, the powder coating composition comprising:

-   -   a) a thermoset resin comprising an acid functional polyester        material,    -   b) a thermoplastic resin and    -   c) a crosslinker,        wherein the coating composition is substantially free of        bisphenol A (BPA), bisphenol F (BPF), bisphenol A diglycidyl        ether (BADGE) and bisphenol F diglycidyl ether (BFDGE).

According to a further aspect of the present invention there is providedfood and/or beverage packaging coated on at least a portion thereof witha powder coating composition, the powder coating composition comprising:

-   -   a) a thermoset resin comprising an acid functional polyester        material,    -   b) a thermoplastic resin and    -   c) a crosslinker,        wherein the coating composition is substantially free of        bisphenol A (BPA), bisphenol F (BPF), bisphenol A diglycidyl        ether (BADGE) and bisphenol F diglycidyl ether (BFDGE).

According to a further aspect of the present invention there is provideda monobloc aerosol can and/or tube coated on at least a portion thereofwith a powder coating composition, the powder coating compositioncomprising:

-   -   a) a thermoset resin comprising an acid functional polyester        material,    -   b) a thermoplastic resin and    -   c) a crosslinker,        wherein the coating composition is substantially free of        bisphenol A (BPA), bisphenol F (BPF), bisphenol A diglycidyl        ether (BADGE) and bisphenol F diglycidyl ether (BFDGE).

All of the features contained herein may be combined with any of theabove aspects and in any combination.

For a better understanding of the invention, and to show how embodimentsof the same may be carried into effect, reference will now be made, byway of example, to the following experimental data.

EXAMPLES

Coating Composition 1

Coating composition 1, containing a thermosetting resin and twothermoplastic resins, was prepared according to the formulation in Table1 and dried using an appropriate method. All amounts in Table 1 aregiven in parts by weight (pbw).

TABLE 1 Coating Composition 1 Coating Composition 1 Thermoplastic resin1 ¹ 24.57 Thermoplastic resin 2 ² 49.14 Thermoset resin ³ 11.60Crosslinker ⁴ 4.25 Pigment 1 ⁵ 2.46 Pigment 2 ⁶ 0.01 Filler ⁷ 4.80Additive 1 ⁸ 0.24 Additive 2 ⁹ 0.09 Additive 3 ¹⁰ 2.83 Total 100.00 ¹Acrylic dispersion (Acrylic dispersion with acid number 30, Mw of 10 kto 30 k; 30% solid dispersed in 70% water) ² Polyolefin dispersion(Polymeric dispersion from Michelman Products, ME 310) ³ Acid functionalpolyester available from PPG Industries, 35 acid value, 100% solidspolyester resin ⁴ PRIMID XL552 available from Ems ⁵ Titanium dioxide ⁶Aluminium dioxide available from Aerox ⁷ BaSO₄ available from CIMBAR ⁸Resiflow PL 200 a flow agent available from Estron Chemical ⁹ Benzoinavailable from Sigma Aldrich ¹⁰ Licowax C available from Clariant

Comparative Coating Composition 1

Comparative coating composition 1 is a polyester-based compositioncontaining a thermoset resin (acid functional polyester available fromPPG Industries, 35 acid value, 100% solids polyester resin), acrosslinker that reacts with acid groups, extender pigments and flowaids. Accordingly, comparative coating composition 1 contains thermosetresins only. The components were extruded via standard powdermanufacturing methods and ground by standard methods.

The properties of the coatings were tested via the following methods.Results are shown in Table 2.

Test Methods

MEK rub test: The number of reciprocating rubs required to remove thecoating was measured using a ball of cotton wool soaked in methyl ethylketone (MEK).

Blush test: Resistance to blush, which is white colouration of the filmcaused by water penetration and entrapment was measured by the followingmethod. The coated panels were sterilised in an autoclave for 1 hour at130° C. in a 1% solution of arylsulphosuccinate detergent in water andthen the film was then observed visually.

Enamel rator: A 1 kg weight was dropped onto a coated panel from a 1meter height to strike an indentation. The test was repeated two timesunder the same conditions on two individual cans. The integrity of thecoating was measured using a WACO Enamel Rater Instrument and a 1% NaClsolution and reported in milliohms (mOhm).

Direct impact: Both tests use a Paul N Garnder Co. falling dart test onmetal panels and references ASTM D 2794-93 test procedure. After thecoating is impacted either directly or reverse impacted it is furthersubjected to Enamel Rator testing.

TABLE 2 Test Results Comparative Coating Coating Composition 1Composition 1 MEK double rubs 100 >100 Blush Pass—no blush Pass—no blushEnamel rater  <3 mOhms  <3 mOhms Direct impact >40 lbs  >40 lbs Reverseimpact >40 lbs  >40 lbs Adhesion  5 B   5 B

The results show that the coating compositions according to the presentinvention perform as well, or better, than the coatings of thecomparative examples.

Attention is directed to all papers and documents which are filedconcurrently with or previous to this specification in connection withthis application and which are open to public inspection with thisspecification, and the contents of all such papers and documents areincorporated herein by reference.

All of the features disclosed in this specification (including anyaccompanying claims, abstract and drawings), and/or all of the steps ofany method or process so disclosed, may be combined in any combination,except combinations where at least some of such features and/or stepsare mutually exclusive.

Each feature disclosed in this specification (including any accompanyingclaims, abstract and drawings) may be replaced by alternative featuresserving the same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

The invention is not restricted to the details of the foregoingembodiment(s). The invention extends to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

1. A powder coating composition comprising: a) a thermoset resincomprising an acid functional polyester material, b) a thermoplasticresin and c) a crosslinker material, wherein the coating composition issubstantially free of bisphenol A (BPA), bisphenol F (BPF), bisphenol Adiglycidyl ether (BADGE) and bisphenol F diglycidyl ether (BFDGE).
 2. Apowder coating composition according to claim 1, wherein the acidfunctional polyester material comprises the reaction product of apolyacid and a polyol.
 3. A powder coating composition according toclaim 2, wherein the polyacid comprises at least 50 mol % terephthalicacid and/or isophthalic acid based on the total number of moles ofpolyacid.
 4. A powder coating composition according to claim 2 or 3,wherein the acid functional polyester is formed from a polyacidcomprising succinic acid, glutaric acid, adipic acid, heptanoic acid,dodecanedioic acid or combinations thereof.
 5. A powder coatingcomposition according to claim 2 or 3, wherein the polyol comprises atleast 10 mol % of neopentyl glycol based on the total number of moles ofpolyol.
 6. A powder coating composition according to any precedingclaim, wherein the acid functional polyester material has an acid number(AN) of at least 25 mg KOH/g.
 7. A powder coating composition accordingto any preceding claim, wherein the thermoplastic resin comprises epoxyresin, polyester resin, polyolefin resin, polyurethane resin,polysiloxane resin, acrylic resin, hydrocarbon resin or combinationsthereof.
 8. A powder coating composition according to claim 7, whereinthe thermoplastic resin comprises polyolefin resin, acrylic resin or acombination thereof.
 9. A powder coating composition according to claim7 or 8, wherein the thermoplastic resin is provided in the form of apowder or in the form of a dispersion in a liquid carrier.
 10. A powdercoating composition according to any preceding claim, wherein the liquidcarrier comprises water.
 11. A powder coating composition according toany preceding claim, wherein the crosslinker comprises ahydroxyalkylamide material and/or a hydroxy functional alkyl polyureamaterial and/or a carbodiimide resin.
 12. A method for producing apowder coating composition comprising: a) a thermoset resin comprisingan acid functional polyester material, b) a thermoplastic resin and c) acrosslinker material, the method comprising the steps of: i) dispersingcomponents (a), (b) and (c) in a liquid carrier, ii) drying thedispersion of step (i) to form a powder, and iii) grinding the powder ofstep (ii) to a particle size of 5 to 300 micron (μm), wherein thecoating composition is substantially free of bisphenol A (BPA),bisphenol F (BPF), bisphenol A diglycidyl ether (BADGE) and bisphenol Fdiglycidyl ether (BFDGE).
 13. A metal substrate coated on at least aportion thereof with a thermoset powder coating composition, the powdercoating composition comprising: a) a thermoset resin comprising an acidfunctional polyester material, b) a thermoplastic resin and c) acrosslinker, wherein the coating composition is substantially free ofbisphenol A (BPA), bisphenol F (BPF), bisphenol A diglycidyl ether(BADGE) and bisphenol F diglycidyl ether (BFDGE).
 14. Food and/orbeverage packaging coated on at least a portion thereof with a thermosetpowder coating composition, the powder coating composition comprising:a) a thermoset resin comprising an acid functional polyester material,b) a thermoplastic resin and c) a crosslinker, wherein the coatingcomposition is substantially free of bisphenol A (BPA), bisphenol F(BPF), bisphenol A diglycidyl ether (BADGE) and bisphenol F diglycidylether (BFDGE).
 15. A monobloc aerosol can and/or tube coated on at leasta portion thereof with a thermoset powder coating composition, thepowder coating composition comprising: a) a thermoset resin comprisingan acid functional polyester material, b) a thermoplastic resin and c) acrosslinker, wherein the coating composition is substantially free ofbisphenol A (BPA), bisphenol F (BPF), bisphenol A diglycidyl ether(BADGE) and bisphenol F diglycidyl ether (BFDGE).